Del Mar is a beach city in San Diego County, California, located on the coast of the Pacific Ocean. Established in 1885 as a seaside resort, the city incorporated in 1959. The population was 3,954 at the 2020 census, down from 4,161 at the 2010 census. The San Diego County Fair is an annual fair held at the Del Mar Fairgrounds. Horse racing is hosted at the Del Mar Racetrack every summer.